One step synthesis of methyl t-butyl ether from t-butanol using hydrogen fluoride-modified zeolite catalysts

ABSTRACT

A method is disclosed wherein t-butanol is reacted with methanol in a reaction zone in one step to provide methyl tert-butyl ether and the improvement of accomplishing the reaction which comprises: a. Using a catalyst consisting of a crystalline aluminosilicate faujasite Y-type zeolite which has been treated with hydrogen fluoride; b. continuously contacting said t-butanol and methanol in a molar amount of about 0.1 to 10 moles of methanol per mole of t-butanol with said catalyst at a temperature of about 20 degrees C. to about 250 degrees C. and a pressure of about atmospheric to about 1000 psig to obtain the methyl tert-butyl ether product wherein the product mix separates into an isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase.

CROSS-REFERENCE

This is a continuation-in-part, of application Ser. No. 07/745,777, filed Aug. 16, 1991, abandoned.

This application is related to U.S. Pat. Nos. 4,827,048, 4,822,921; 5,099,072; 5,059,725 and 5,081,318 and to application Ser. No. 07/724,071 and allowed 07/917,218.

This invention concerns an improved process for preparing methyl tertiary-butyl ether (MTBE) by the reaction of tertiary butanol and methanol in the presence of a catalyst comprising a hydrogen fluoride-modified zeolite. The invention is particularly advantageous in that the reaction takes place in one-step, typically MTBE is generated continuously in 30+% concentration in the crude liquid product, with the crude product mix separating into an isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase.

BACKGROUND OF THE INVENTION

It is known to those skilled in the art that ethers, including unsymmetrical ethers, may be prepared by reacting an alcohol with another alcohol to form the desired product. The reaction mixture, containing catalyst and/or condensing agent may be separated and further treated to permit attainment of the desired product. Such further treatment commonly includes one or more distillation operations.

Methyl tert-butyl ether is finding increasing use as a blending component in high octane gasoline as the current gasoline additives based on lead and manganese are phased out. Currently all commercial processes for the manufacture of methyl tert-butyl ether are based upon the liquid-phase reaction of isobutylene and methanol (Eq. 1), catalyzed by a cationic ion-exchange resin (see, for example: Hydrocarbon Processing, October 1984, p. 63; Oil and Gas J., Jan. 1, 1979, p. 76; Chem. Economics Handbook-SRI, September 1986, p. 543-7051P). The cationic ion-exchange resins used in MTBE synthesis normally have the sulphonic acid functionality (see: J. Tejero, J. Mol. Catal., 42 (1987) 257; C. Subramamam et al., Can. J. Chem. Eng., 65 (1987) 613). ##STR1##

With the expanding use of MTBE as an acceptable gasoline additive, a growing problem is the availability of raw materials. Historically, the critical raw material is isobutylene (Oil and Gas J., Jun. 8, 1987, p. 55). It would be advantageous, therefore, to have a process to make MTBE that does not require isobutylene as a building block. It would be advantageous to have an efficient process for making MTBE by reaction of methanol with tertiary butyl alcohol, since t-butanol (TBA) is readily available commercially through isobutane oxidation.

In U.S. Pat. No. 4,144,138 (1979) to Rao et al., there is disclosed a method for recovering methyl tertiary butyl ether from etherification reaction effluent by azeotropic distillation to recover methanol-ether azeotrope overhead which is water-washed to give pure ether raffinate, the latter being azeotropically distilled to yield ether-methanol overhead which is recycled to water washing.

The preparation of methyl tert-butyl ether from methyl I5 and tert-butyl alcohols is discussed in S. V. Rozhkov et al., Prevrashch Uglevodorodov, Kislotno-Osnovn. Geterogennykh Katal. Tezisy Dokl. Vses Konf., 1977, 150 (C. A. 92:58165y). Here the TBA and methanol undergo etherification over KU-2 strongly acidic sulfopolystyrene cation-exchangers under mild conditions. This reference contains data on basic parameters of such a process. It is also pointed out that, although a plant for etherification over cation exchangers does not present any major problems, considerations include the fact that recycling large amounts of tert-butyl alcohol and methanol, as well as isobutylene, causes the scheme to be somewhat more expensive. Also, the progress of the reaction over cation exchangers is usually complicated by various adsorption and diffusion factors, by swelling phenomena, and by the variable distribution of the components between the solution and ion-exchanger phase. Furthermore, said acidic cation-exchangers with an organic (polystyrene or polymethacrylate) backbone generally have a very limited stability range with regard to operating temperatures, with temperatures above 120° C. normally leading to irreversible destruction of the resin and loss of catalytic activity.

In U.S. Pat. No. 2,282,469 to Frolich there is disclosed a process for preparing methyl tertiary butyl ether over a catalyst comprising Kieselguhr impregnated with phosphoric acid at a temperature of about 175° F. to 350° F.

Japanese Patent 0007432 teaches the use of zeolites to make dialkyl ethers containing primary or secondary alkyl groups. The zeolites have a porous structure and are represented by:

    M.sub.2/n O.Al.sub.2 O.sub.3.xSiO.sub.2..sub.y H.sub.2 O

where M is an alkali metal or alkaline earth metal cation or organic base cation, n is the valence of the cation and x and y are variables.

U.S. Pat. No. 4,058,576 to Chang et al. teaches the use of (pentasil-type) aluminosilicate zeolites, such as ZSM-5, having a pore size greater than 5 angstrom units and a silica-to-alumina ratio of at least 12, to convert lower alcohols to a mixture of ethers and olefins.

In U.S. Pat. No. 4,822,921 there is disclosed a method for producing MTBE by reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising an inert support, such as titania, having a phosphoric acid impregnated thereon.

U.S. Pat. No. 4,827,048 discloses a method for producing MTBE by reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising a heteropoly acid such as 12-tungstophosphoric acid or 12-molybdophosphoric acid on an inert support, such as titania.

In copending U.S. patent application Ser. No. 07/494,281, there is disclosed a method for preparing methyl tertiary butyl ether by reacting butanol and methanol in the presence of a catalyst comprising a super-acid alumina or a faujasite-type zeolite.

Copending U.S. patent application Ser. No. 07/494,280 discloses the reaction of butanol and methanol in the presence of acidic montmorillonite clay catalysts having certain identifiable physical parameters.

Copending U.S. patent application Ser. No. 07/677,192 discloses a super acid, sulfuric acid-on-Group IV oxide for preparing MTBE from t-butanol and methanol in one step. In copending U.S. patent application Ser. No. 07/663,527, a Y-type zeolite modified with fluorosulfonic acid is disclosed.

Copending U.S. patent application Ser. No. 07/724,071, there is disclosed a method for one-step synthesis of MTBE from t-butanol using fluorocarbon sulfonic acid polymers on inert supports.

It would be a substantial advance in the art if methyl tertiary butyl ether could be selectively synthesized from tertiary butyl alcohol and methanol in one step using a catalyst which allows for rapid conversion of t-butanol. It has now been discovered that hydrogen fluoride-modified zeolites can be used as catalysts for the selective synthesis of methyl tertiary butyl ether from tertiary butyl alcohol and methanol. The accompanying examples demonstrate good yields of MTBE when using the modified zeolites of the instant invention for such a reaction.

SUMMARY OF THE INVENTION

In accordance with certain of its aspects, the novel method of this invention for preparing methyl tert-butyl ether from tertiary butyl alcohol (t-butanol) and methanol in one-step comprises reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising a hydrogen fluoride-modified zeolite at an elevated temperature and moderate pressure. Examples demonstrate particularly the effectiveness of a hydrogen fluoride-modified rare earth exchanged Y-zeolite.

DESCRIPTION OF THE INVENTION

Preparation of the product of this invention may be carried out typically by reacting tertiary butyl alcohol and methanol in the presence of an etherification catalyst. The etherification is carried out in one step and the catalyst preferably comprises a rare earth exchanged Y-zeolite modified with hydrogen fluoride.

The reaction can be represented by the following: ##STR2##

Generally the methanol and t-butanol coreactants may be mixed in any proportion in order to generate the desired methyl t-butyl ether, but preferably the molar ratio of methanol to t-butanol in the feed mixture should be about 0.1 to 10 if the yield of desired MTBE is to be maximized. In order to achieve maximum selectivity to MTBE, and optimum conversion per pass, an excess of methanol in the liquid feed is desirable. The most preferred methanol-to-tertiary butanol molar ratio is from 1:1 to 5:1.

In certain circumstances, it may be particularly desirable that the TBA conversion be high enough (e.g. 80% or greater), such that the crude product mix phase separates into an isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase. Preferably such a product phase separation would be achieved at as low an etherification temperature as possible, but particularly in the range 160°-200° C.

The synthesis of Eq. 2 can also be conducted where the t-butanol and methanol reactants are mixed with certain other components including water, ketones such as acetone, peroxides and hydroperoxides such as di-t-butyl peroxide and allyl t-butyl peroxide, as well as esters such as t-butyl formate. Typically each of said classes of components makes up less than 10% of the total feed mixture.

The same process may also be applied to the preparation of other alkyl tertiary alkyl ethers. For example, said process may be applied to the reaction of a C₁ -C₆ primary alcohol such as methanol, ethanol, n-propanol and n-hexanol with a C₄ -C₁₀ tertiary alcohol such as, for example, tertiary butanol and tertiary amyl alcohol. Reaction of methanol with tertiary amyl alcohol (2-methyl-2-butanol) would then yield methyl tertiary amyl ether (TAME). Alternatively a mixture of alcohols, e.g., a mixture of C₁ -C₅ alcohols, could be reacted to give a mixture of alkyl tert-alkyl ethers.

Good results were realized using certain crystalline aluminosilicate zeolites as catalysts for the reaction represented in Equation 2, particularly the isostructural group of faujasite zeolites that include the synthetic Y-zeolites. The preferred Y-zeolites are the rare earth exchanged Y-zeolites.

The unit cells of zeolites X and Y are cubic, a_(o) ≈2.5 nm, and each contains 192 silicon- or aluminum-centered oxygen tetrahedra which are linked through shared oxygen atoms. Because of the net negative charge on each of the aluminumcentered tetrahedra, each unit cell contains an equivalent number of charge-balancing cations. These are exclusively sodium ions in zeolites in their synthesized form. Typical cell contents for the Y-zeolites in the hydrated form are:

    Na.sub.56 [(A10.sub.2).sub.56 (SiO.sub.2).sub.136 ]. 250 H.sub.2 O

Y-zeolites are distinguished on the basis of the relative concentration of silicon and aluminum atoms and the consequent effects on detailed structure and related chemical and physical properties. The aluminum atoms in the unit cell of Y-zeolite vary from 76 to 48 giving a Si:Al ratio between 1.5 and 3.0. Both the cation concentration and charge density on the aluminosilicate structure are lower for Y-zeolites than for X-zeolites, where the aluminum atoms in the unit cell vary from 96 to 77.

The feature which determines the difference between faujasites and other zeolites built up from sodalite units is the double 6-membered ring or hexagonal prism, by which the units are linked. The sodalite unit, or β-cage, can be represented by a truncated octahedron, with the 24 silicon or aluminum atoms (designated T atoms) taking positions at the vertices. The 36 oxygen atoms are displaced from the midpoints of the edges joining the vertices in order to attain tetrahedral configuration around the T atoms. The free diameter of the void within the β-cage is 0.66 nm, but only the smallest molecules can enter through the 0.22 nm diameter opening in the distorted ring of six oxygen atoms associated with each hexagonal face. Each sodalite unit is linked tetrahedrally across hexagonal faces by six bridging oxygens to four other sodalite units. The larger void spaces enclosed by sodalite units and hexagonal prisms are termed α-cages, or supercages. The α-cage is a 26-hedron with a free diameter of ≈1.3 nm, and it can be entered through four distorted 12-member rings of diameter 0.80-0.90 nm. In this way each α-cage is tetrahedrally joined to four others giving a complex system of void space extending throughout the zeolite structure. The α- and β-cages together give Y-zeolites, along with X-zeolites, the largest void volume of any known zeolites, which is ca. 50 vol % of the dehydrated crystal. From the catalytic viewpoint, the α-cages are by far the most important, since, unlike the β-cages, they permit entry of numerous aliphatic and aromatic compounds.

Particularly effective in the subject synthesis of MTBE are the synthetic Y-zeolites. Preferably said zeolites should be in a strongly acidic form whereby some, or all, of the cations (Group I or II, alkali or alkaline earth metal ions such as sodium, potassium, calcium or magnesium) are exchanged by protons either through ammonium exchange followed by thermal stabilization (deammoniation, removal of NH₃) at elevated temperatures (e.g. 400°-500° C.) through mineral acid treatment, etc. Alternatively, said Y-zeolites may be dealuminized by hydrothermal treatment, by mineral acid treatment or by treatment with ethylenediaminetetraacetic acid (EDTA) or other chelating agents, in which case said dealuminized Y-zeolites should have a Si:Al ratio of greater than three. A further possibility is that said Y-zeolites may be rare-earth exchanged with, for example, a mixture of rare-earth salts, by treatment with lanthanum salts, etc. Said rare-earth exchanged Y-zeolites would then have a Si:Al ratio of 1.5 to 3. The exchange of the sodium ions of the Y-zeolite by rare earth ions has been reviewed (see, for example, R. Rudham and A. Stockwell, The Chemical Society Specialist Periodical Report--Catalysis, Vol. I, 1977, Chapter 3).

Illustrative of suitable Y-zeolites for the practice of this invention include Linde SK-500, a rare-earth exchanged Y-zeolite, having a Si:Al ratio of 1.5→2 and 10-20% added alumina binder, and PQ Corporation's CP 304-37, a thermally-stabilized, ammonium-exchanged Y-zeolite having a silica:alumina ratio of ca. 11:1, with a silica-alumina binder, as well as CP 316-26, another ammonium exchanged Y-zeolite this time having a silica-to-alumina ratio of 80.

The hydrogen fluoride-modified zeolite is prepared by treating the Y-zeolite or dealuminized Y-zeolite with hydrogen fluoride, with an aqueous solution of hydrofluoric acid, or with a solution of HF in a suitable organic solvent. Preferably the hydrogen fluoride is added to said zeolite as a solution of hydrofluoric acid in distilled water. The aqueous solution of hydrofluoric acid in distilled water or other suitable solvent should be greater than 1N and preferably from about 5N to 30N. Example 1 demonstrates the effective use of an 24N solution of HF. Methods of preparing these HF-modified catalysts are illustrated in the accompanying Examples 1 to 3.

Said catalysts may be in the form of powders, pellets, granules, spheres, shapes and extrudates. The examples described herein demonstrate the advantages of using extrudates.

The reaction may be carried out in either a stirred slurry reactor or in a fixed bed continuous flow reactor. The catalyst concentration should be sufficient to provide the desired catalytic effect.

Etherification can generally be conducted at temperatures from 20° to 250° C.; the preferred range is 80° to 200° C. The total operating pressure may be from 0 to 1000 psig, or higher. The preferred pressure range is 50 to 500 psig.

Typically, MTBE is generated continuously in up to ca. 35 wt % concentration or greater in the crude liquid product at total liquid hourly space velocities (LHSV) of up to 6 or higher and relatively mild conditions, where: ##EQU1##

The examples which follow illustrate the one-step synthesis of MTBE from TBA and MeOH (Eq. 2) using hydrogen fluoride-treated Y-type zeolites particularly the form of extrudates. The examples are only intended as a means of illustration and it is understood the invention is not meant to be limited thereby.

Conversions of t-butanol (TBA, wt %) are estimated in the following examples using the equation: ##EQU2##

Selectivities of methyl t-butyl ether (MTBE, mole %) and isobutylene (C₄ H₈, mole %) are estimated from: ##EQU3## It may be noted that: 1) Comparing etherification data in Table I and Example 4, using the hydrogen fluoride-treated zeolite Linde SK-500, prepared by the method of Example 1, with data for SK-500 extrudates alone (Comparative Example A or Table IV) it is seen that:

a) The tBA conversion levels with the HF-treated zeolites of Example 4 at all operating temperatures, but particularly at 140° to 160° C., are measurably higher than for SK-500 alone.

b) Only the HF-modified zeolite of Example 4 achieves product phase separation into an isobutylene-MTBE product rich phase and a heavier aqueous methanol phase at the 160° C. operating temperature.

Comparing etherification data in Example 5 and Table II, using the HF-treated zeolite, CP-304-37 of Example 2, with data for CP-304-37 extrudate alone (Comparative Example B or Table V) it may be noted that:

a) While the tBA conversion levels with both the HF-treated zeolite and the untreated CP-304-37 are similar, and near equilibrium, at the lower temperatures (e.g. 100°-140° C.),

b) only the HF-treated zeolite gives product phase separation into an isobutylene-MTBE rich phase and a heavier aqueous methanol phase at the 160° C. operating temperature. Of note, comparative Example B of this invention is also included in related, copending U.S. patent application Ser. No. 07/494,281.

3) Generally an excellent performance is also realized in Example 6 for the HF-treated zeolite CP-316-26, prepared by the method of Example 3. Etherification data are summarized in Table III. Again product phase separation is achieved at 160° C. operating temperature.

4) In Example 7, the HF-modified Y-zeolite of Example 1 provided excellent etherification activity over 23 days of operation using a crude tBA/MeOH feedstock also containing water, MTBE, isopropanol, acetone, di-t-butyl peroxide and t-butyl formate (see Table VI).

EXAMPLE 1

This example illustrates the preparation of a hydrogen fluoride-modified Y-zeolite.

To 100 g of Y-zeolite (Linde SK-500, a rare-earth exchanged Y-zeolite having a Si:Al ratio of 1.5→2 and 10-20% added alumina binder, in 1/16" diameter extrudated form) was added a solution of 48% hydrofluoric acid (50 g) 24N in distilled water (100 g). The mixture was stirred for 24 hours under nitrogen, filtered and the solids washed with distilled water and dried in vacuo at 40° C., overnight, and at 150° C. for 4 hours.

The recovered white extrudates were found to contain on analysis:

F⁻, 6.30%

H₂ O, 0.76%

Acidity, 0.15 meq/g

EXAMPLES 2 AND 3

The examples illustrate the preparation of two other hydrogen fluoride-modified Y-zeolites.

Following the procedures of Example 1, two Y-zeolites:

a) CP-304-37, a thermally-stabilized, ammonium exchanged Y-zeolite from PQ Corporation having a silica:alumina ratio of Ca. 11:1, with 80% silica-alumina binder (SiO₂ :Al₂ O₃ ratio 16:84), in 1/16" diameter extruded form, and

b) CP-316-26, an ammonium exchanged Y-zeolite from PQ Corporation having a silica-to-alumina ratio of 80, also in 1/16" diameter extruded form,

were treated with hydrofluoric acid, washed and dried in vacuo. The recovered extrudates were found to contain:

    ______________________________________                                         Example 2: (HF/CP-304-37):                                                                              F.sup.-, 1.78%                                                                 H.sub.2 O, 0.14%                                                               Acidity, 0.024 meq/g                                  Example 3: (HF/CP-316-26):                                                                              F.sup.-, 4.65%                                                                 H.sub.2 O, 1.86%                                                               Acidity, 0.085 meq/g                                  ______________________________________                                    

EXAMPLE 4

This example illustrates the production of methyl t-butyl ether from t-butanol and methanol using a hydrogen fluoride-modified Y-zeolite.

Synthesis was conducted in a tubular reactor (1/2" id, 12" long), constructed of 316 stainless steel, operated upflow and mounted in a furnace controllable to ±1.0° C. and fitted with pumps allowing flow control to <±1 cc/hr. The reactor was also fitted with a pressure regulating device and equipment for monitoring temperature, pressure and flow rate.

The reactor was charged at the beginning of the experiment with 25 cc hydrogen fluoride treated Y-zeolite extrudates prepared by the method of Example 1. A screen of glass wool was placed at the top and bottom of the reactor to ensure the catalyst would remain in the middle portion.

The catalyst bed was treated with a methanol/t-butanol (1.1:1 molar mix) upflow, at a flow rate of 50 cc/hr, while the reactor was held at 120° C., with a total pressure of 300 psi. Samples of crude product effluent were collected periodically on-stream, in 316 ss bombs, and analyzed by glc and gc-ir.

Typical analyses data for samples taken under these conditions are summarized in Table I. Performance at a series of other temperatures (140°, 160°, 180° C.) and flow rates (160 cc/hr) was determined using the same procedures. These results are given in Table I. Of note, t-butanol conversion levels and isobutylene/MTBE selectivities at 140° C. and 160° C. are as follows:

    ______________________________________                                                                     Molar                                                     Operating                                                                              TBA          Selectivity (%)                                    Sample   Temp (°C.)                                                                        Conv. (%)    C.sub.4 H.sub.8                                                                     MTBE                                      ______________________________________                                         3        140       67           32   64                                        5        160       84           .sup.a                                                                              .sup.a                                    ______________________________________                                          .sup.a Not Determined                                                    

Product phase separation into a isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase was achieved at both the 160° C. and 180° C. operating temperatures.

EXAMPLE 5

This example illustrates the production of methyl t-butyl ether from t-butanol and methanol using another hydrogen fluoride-modified Y-zeolite.

Following the procedures of Example 4, the reactor was charged with 25 cc of the hydrogen fluoride treated Y-zeolite of Example 2 and performance was monitored over a series of temperatures (100°-180° C.) and feed rates (LHSV=2→5). The results are summarized in Table II.

Calculated tBA conversions and C₄ H₈ /MTBE selectivities are as follows:

    ______________________________________                                                                     Molar                                                     Operating                                                                              TBA          Selectivity (%)                                    Sample   Temp (°C.)                                                                        Conv. (%)    C.sub.4 H.sub.8                                                                     MTBE                                      ______________________________________                                         6        140       71           32   63                                        7        160       89           .sup.a                                                                              .sup.a                                    ______________________________________                                          .sup.a Not Determined                                                    

EXAMPLE 6

This example illustrates the production of methyl t-butyl ether from t-butanol and methanol using another hydrogen-modified Y-zeolite.

Following the procedures of Example 4, the reactor was charged with 25 cc of the hydrogen fluoride-treated Y-zeolite of Example 3 and performance was monitored over a series of temperatures (120°-180° C.) and feed rates (LHSV=2→6). The results are summarized in Table III.

Calculated tBA conversions and C₄ H₈ /MTBE selectivities are as follows:

    ______________________________________                                                                     Molar                                                     Operating                                                                              TBA          Selectivity (%)                                    Sample   Temp (°C.)                                                                        Conv. (%)    C.sub.4 H.sub.8                                                                     MTBE                                      ______________________________________                                         3        140       70           29   68                                        6        160       86           .sup.a                                                                              .sup.a                                    ______________________________________                                          .sup.a Not Determined                                                    

COMPARATIVE EXAMPLE A

This comparative example illustrates the performance of an unmodified Y-zeolite in the production of methyl t-butyl ether from t-butanol and methanol over a range of conditions.

Using the equipment and procedures of Example 4, 25 cc of Y-zeolite (Linde SK-500, 1/16" diameter extrudates) was charged to the reactor system and performance was monitored over a range of operating temperatures (100°-180° C.) and flow rates (50-60 cc/hr). The results are summarized in Table IV.

Calculated tBA conversion and C₄ H₈ /MTBE selectivities at 140° and 160° C. are typically as follows:

    ______________________________________                                                                     Molar                                                     Operating                                                                              TBA          Selectivity (%)                                    Sample   Temp (°C.)                                                                        Conv. (%)    C.sub.4 H.sub.8                                                                     MTBE                                      ______________________________________                                         6        140       56           35   64                                        8        160       78           59   39                                        ______________________________________                                    

COMPARATIVE EXAMPLE B

This comparative example illustrates the performance of another unmodified Y-zeolite in the production of methyl t-butanol and methanol.

Using the equipment and procedures of Example 4, 25 cc of Y-zeolite (CP-304-37, 1/16" extrudates) was charged to the reactor system and performance was monitored over a range of operating temperatures (100°-180° C.) and flow rates (50-160 cc/hr). The results are summarized in Table V.

Calculated tBA conversions and C₄ H₈ /MTBE selectivities at 140° and 160° C. are typically as follows:

    ______________________________________                                                                     Molar                                                     Operating                                                                              TBA          Selectivity (%)                                    Sample   Temp (°C.)                                                                        Conv. (%)    C.sub.4 H.sub.8                                                                     MTBE                                      ______________________________________                                         6        140       72           35   62                                        7        160       81           64   39                                        ______________________________________                                    

EXAMPLE 7

This example illustrates the performance of a HF-treated Y-zeolite in the production of methyl t-butyl ether from a crude t-butanol/methanol feedstock over an extended period.

Using the unit configuration and procedures of Example 4, 50 cc of the HF-treated SK-500 catalyst of Example 1 was charged to a 100 cc capacity reactor system and performance was monitored over 23 days at 140° C. using a crude feed mix comprising t-butanol, methanol, water, MTBE, acetone, isopropanol, di-t-butyl peroxide and t-butyl formate. The methanol to t-butanol molar feed ratio was 2:1, the feed rate was maintained at 100 cc/hr. The results are summarized in Table VI.

Calculated tBA conversions are C₄ H₈ /MTBE selectivities for typical samples are as follows:

    ______________________________________                                                                     Molar                                                     Operating                                                                              TBA          Selectivity (%)                                    Sample   Temp (°C.)                                                                        Conv. (%)    C.sub.4 H.sub.8                                                                     MTBE                                      ______________________________________                                         3R        7        34           33   68                                        10       23        33           25   72                                        ______________________________________                                    

                                      TABLE I                                      __________________________________________________________________________                            Time                                                            MeOH/TBA   Feed                                                                               On                                                              Molar  Temp.                                                                              Rate                                                                               Stream                                                                             ←PRODUCT COMPOSITION (WT %)→            Ex.                                                                               Catalyst                                                                            Ratio  (°C.)                                                                       (cc/hr)                                                                            (Days)                                                                             SAMPLE  H.sub.2 O                                                                         MeOH                                                                               C.sub.2 4.sub.8                                                                   TBA                                                                               MTBE                           __________________________________________________________________________     4  Ex. 1                                                                               1.1                FS-1       33.5   66.2                                             120 50  1   1       8.4                                                                               23.6                                                                               7.0                                                                               33.1                                                                              27.6                                                      2       8.2                                                                               24.0                                                                               7.2                                                                               30.5                                                                              29.8                                          140 50  2   →3                                                                              11.2                                                                              22.4                                                                               10.7                                                                              21.9                                                                              33.6                                                      4       11.8                                                                              22.2                                                                               10.0                                                                              22.4                                                                              33.3                                                               7.6                                                                               20.2                                                                               31.2                                                                              10.6                                                                              30.1                                         160 50  3   →5                                                                              29.2                                                                              39.5                                                                               7.0                                                                               10.2                                                                              13.7                                                      6          21.4                                                                               29.4                                                                              11.1                                                                              29.3                                                               8.6                                                                               37.8                                                                               6.8                                                                               9.9                                                                               13.4                                                             31.8                                                                            0.9                                                                               6.6                                                                                61.3                                                                              2.5                                                                               28.4                                         180 50  4   7                                                                                      29.2                                                                              53.7                                                                               5.9                                                                               5.3                                                                               5.6                                                       8          8.5 69.0                                                                              4.4                                                                               16.5                                                               1.4                                                                               51.9                                                                               5.7                                                                               5.3                                                                               8.2                                                              28.5                                                       160 160 5   9       9.5                                                                               25.5                                                                               13.5                                                                              27.6                                                                              23.6                                                      10      9.7                                                                               25.3                                                                               13.8                                                                              27.1                                                                              23.8                           __________________________________________________________________________      .sup.a Linde SK500 treated with HF                                       

                                      TABLE II                                     __________________________________________________________________________                            Time                                                            MeOH/TBA   Feed                                                                               On                                                              Molar  Temp.                                                                              Rate                                                                               Stream                                                                             ←PRODUCT COMPOSITION (WT %)→            Ex.                                                                               Catalyst                                                                            Ratio  (°C.)                                                                       (cc/hr)                                                                            (Days)                                                                             SAMPLE  H.sub.2 O                                                                         MeOH                                                                               C.sub.2 4.sub.8                                                                   TBA                                                                               MTBE                           __________________________________________________________________________     5  Ex. 2                                                                               1.1                FS-1       33.6   66.1                                             100 50  1   1       3.4                                                                               28.7                                                                               2.5                                                                               49.8                                                                              15.2                                                      2       3.8                                                                               28.6                                                                               2.5                                                                               50.0                                                                              14.9                                          120  1  2   3       9.5                                                                               22.4                                                                               6.3                                                                               28.4                                                                              33.1                                                      4       9.2                                                                               22.1                                                                               6.6                                                                               26.5                                                                              35.3                                          140 50  3   5       11.7                                                                              21.6                                                                               11.3                                                                              19.2                                                                              35.9                                                      →6                                                                              11.8                                                                              21.6                                                                               11.4                                                                              19.0                                                                              35.5                                                               4.0                                                                               15.4                                                                               43.1                                                                              6.9                                                                               30.3                                         160 50  4   →7                                                                              30.8                                                                              44.8                                                                               5.7                                                                               7.8                                                                               10.5                                                               3.9                                                                               15.4                                                                               43.3                                                                              7.2                                                                               29.9                                                     8                                                                                      31.4                                                                              43.6                                                                               5.8                                                                               8.0                                                                               10.8                                                               1.1                                                                               7.5                                                                                71.8                                                                              2.5                                                                               16.7                                         180 50  5   9                                                                                      29.3                                                                              55.5                                                                               5.2                                                                               5.1                                                                               4.4                                                                0.9                                                                               7.1                                                                                73.7                                                                              2.4                                                                               15.8                                                     10                                                                                     29.6                                                                              55.3                                                                               5.1                                                                               5.1                                                                               4.4                                           160 125 6   11      10.4                                                                              25.3                                                                               15.5                                                                              21.8                                                                              26.8                                                      12      10.8                                                                              25.0                                                                               15.1                                                                              23.0                                                                              25.9                           __________________________________________________________________________      .sup.a PQ's CP304-37 treated with HF                                     

                                      TABLE III                                    __________________________________________________________________________                            Time                                                            MeOH/TBA   Feed                                                                               On                                                              Molar  Temp.                                                                              Rate                                                                               Stream                                                                             ←PRODUCT COMPOSITION (WT %)→            Ex.                                                                               Catalyst                                                                            Ratio  (°C.)                                                                       (cc/hr)                                                                            (Days)                                                                             SAMPLE  H.sub.2 O                                                                         MeOH                                                                               C.sub.2 H.sub.8                                                                   TBA                                                                               MTBE                           __________________________________________________________________________     6  Ex. 3                                                                               1.1                FS-1       33.6   66.1                                             120 50  1   1       9.7                                                                               21.0                                                                               5.7                                                                               26.8                                                                              36.5                                                      2       9.3                                                                               21.9                                                                               5.4                                                                               28.8                                                                              34.4                                          140 50  2   →3                                                                              11.5                                                                              20.9                                                                               10.0                                                                              20.0                                                                              37.3                                                      4       11.5                                                                              21.0                                                                               10.1                                                                              20.0                                                                              37.1                                                               7.0                                                                               19.9                                                                               31.6                                                                              9.8                                                                               31.5                                         160 50  3   5                                                                                      30.9                                                                              40.9                                                                               6.2                                                                               9.0                                                                               12.7                                                               6.4                                                                               18.7                                                                               34.2                                                                              9.4                                                                               31.0                                                     →6                                                                              29.6                                                                              40.7                                                                               6.4                                                                               9.6                                                                               13.3                                                               1.6                                                                               8.7                                                                                65.7                                                                              3.8                                                                               18.4                                         180 50  4   7                                                                                      30.2                                                                              53.5                                                                               5.1                                                                               5.4                                                                               5.4                                                                1.2                                                                               7.6                                                                                62.8                                                                              3.0                                                                               24.6                                                     8                                                                                      30.5                                                                              52.3                                                                               5.5                                                                               5.5                                                                               5.8                                           160 160 5   9       13.0                                                                              24.2                                                                               19.6                                                                              14.2                                                                              28.7                                                      10      12.8                                                                              24.0                                                                               19.4                                                                              14.3                                                                              28.9                           __________________________________________________________________________      .sup.a PQ's CP316-26 treated with HF                                     

                                      TABLE IV                                     __________________________________________________________________________                            Time                                                            MeOH/TBA   Feed                                                                               On                                                              Molar  Temp.                                                                              Rate                                                                               Stream                                                                             ←PRODUCT COMPOSITION (WT %)→            Ex.                                                                               Catalyst                                                                            Ratio  (°C.)                                                                       (cc/hr)                                                                            (Days)                                                                             SAMPLE  H.sub.2 O                                                                         MeOH                                                                               C.sub.4 H.sub.8                                                                   TBA                                                                               MTBE                           __________________________________________________________________________     A  SK-500                                                                              1.1                FS         31.4   68.2                                             100 50  1   1        4.2                                                                              25.2                                                                               4.5                                                                               49.3                                                                              16.6                                                      2        3.6                                                                              25.3                                                                               4.1                                                                               51.0                                                                              15.9                                          120 50  2   3        8.3                                                                              21.5                                                                               6.9                                                                               36.3                                                                              26.9                                                      4        8.6                                                                              21.0                                                                               7.7                                                                               34.0                                                                              28.7                                          140 50  3   5       11.0                                                                              17.6                                                                               10.0                                                                              26.7                                                                              34.6                                                      →6                                                                              11.3                                                                              19.0                                                                               11.8                                                                              23.5                                                                              34.3                                          160 50  4   7       12.9                                                                              21.4                                                                               24.7                                                                              15.2                                                                              25.5                                                      →8                                                                              13.5                                                                              22.2                                                                               24.0                                                                              14.9                                                                              25.1                                                               14.1                                                                              31.6                                                                               10.4                                                                              8.8                                                                               35.1                                         180 50  5   9                                                                                      31.8                                                                              41.4                                                                               7.1                                                                               7.5                                                                               11.5                                                               17.0                                                                              31.7                                                                               17.0                                                                              7.3                                                                               27.2                                                     10                                                                                     30.0                                                                              38.8                                                                               8.0                                                                               8.6                                                                               14.1                                                       11      10.0                                                                              22.2                                                                               13.1                                                                              29.7                                                                              24.9                                         160 160 6                                                                                  12       9.8                                                                              22.1                                                                               13.1                                                                              29.9                                                                              25.0                           __________________________________________________________________________

                                      TABLE V                                      __________________________________________________________________________                             Time                                                            MeOH/TBA   Feed                                                                               On                                                              Molar  Temp.                                                                              Rate                                                                               Stream                                                                             ←PRODUCT COMPOSITION (WT %)→           Ex.                                                                               Catalyst                                                                             Ratio  (°C.)                                                                       (cc/hr)                                                                            (Days)                                                                             SAMPLE  H.sub.2 O                                                                         MeOH                                                                               C.sub.4 H.sub.8                                                                   TBA                                                                               MTBE                          __________________________________________________________________________     B  CP-304-37.sup.a                                                                      1.1                FS         30.1   69.6                                             100 50  1   1       2.7                                                                               26.7                                                                               3.1                                                                               54.2                                                                              13.2                                                      2       3.3                                                                               25.4                                                                               3.3                                                                               52.3                                                                              15.7                                          120 50  2   3       8.2                                                                               18.7                                                                               7.7                                                                               29.8                                                                              35.5                                                      4       9.6                                                                               17.8                                                                               7.7                                                                               26.4                                                                              38.4                                          140 50  3   5       11.0                                                                              17.9                                                                               13.5                                                                              19.5                                                                              37.5                                                      →6                                                                              11.1                                                                              18.1                                                                               13.5                                                                              19.3                                                                              37.3                                          160 50  4   →7                                                                              10.8                                                                              20.8                                                                               28.7                                                                              13.3                                                                              26.0                                                      8       8.7                                                                               19.6                                                                               27.2                                                                              13.8                                                                              28.5                                                               26.1                                                                              45.5                                                                               6.3                                                                               7.3                                                                               14.3                                         180 50  5   9                                                                                      28.0                                                                              46.0                                                                               6.7                                                                               7.3                                                                               11.7                                                               23.8                                                                              41.3                                                                               10.7                                                                              6.6                                                                               16.6                                                     10                                                                                     28.0                                                                              48.3                                                                               5.4                                                                               7.2                                                                               11.2                                          160 125 6   11      7.0                                                                               23.0                                                                               10.4                                                                              36.6                                                                              22.9                                                      12      7.4                                                                               23.1                                                                               10.6                                                                              35.3                                                                              23.6                          __________________________________________________________________________

                                      TABLE VI                                     __________________________________________________________________________                           Time                                                        CAT-                                                                               MeOH/tBA       On  ←PRODUCT COMPOSITION (WT %)                        A-  Molar  Temp.   Steam                                                                              Sam-                                                 Ex.                                                                               LYST                                                                               Ratio  (°C.)                                                                       LHSV                                                                               (Days)                                                                             ple H.sub.2 O                                                                         MeOH                                                                               C.sub.4 H.sub.8                                                                   Ac.sub.2 O                                                                         2-PrOH                                                                              tBA                                                                               MTBE                                                                               DTBP                                                                               TBF                __________________________________________________________________________     7  Ex. 1                                                                              2:1                FS  5.2                                                                               40.8   0.6 1.5  49.3                                                                              2.5 4.8 0.18                             140 2    7  →3R                                                                         9.5                                                                               35.2                                                                               4.1                                                                               1.0 1.5  32.7                                                                              16.0                                                                               4.2 0.01                             140 2    9  .sup.  4R                                                                          10.0                                                                              34.7                                                                               3.7                                                                               1.0 1.4  30.7                                                                              18.4                                                                               4.0 0.01                             140 2   16  6   9.2                                                                               35.2                                                                               3.3                                                                               1.0 1.4  33.2                                                                              16.5                                                                               3.9 0.01                             140 2   21  9   9.8                                                                               35.6                                                                               3.1                                                                               1.0 1.4  32.8                                                                              16.1                                                                               3.7 0.01                             140 2   23  →10                                                                         9.7                                                                               35.2                                                                               3.1                                                                               1.0 1.4  32.8                                                                              16.6                                                                               3.8 0.01               __________________________________________________________________________ 

What is claimed is:
 1. In a method wherein t-butanol is reacted with methanol in one step in the presence of a catalyst to provide methyl tert-butyl ether (MTBE), the improvement comprising using as a catalyst a rare earth exchanged crystalline aluminosilicate faujasite-type Y-zeolite having a silica to alumina ratio of 1.5 to 3 modified with an aqueous solution of hydrogen fluoride of 1 to 30N, and continuously contacting said t-butanol and methanol in a molar amount of about 0.1 to 10 moles of methanol per mole of t-butanol with said catalyst at temperatures of 160° C. and 180° C. and a pressure of about atmospheric to about 1000 psig to obtain methyl tert-butyl ether product, wherein the product comprises a two-phase mix of an isobutylene-MTBE product-rich phase and a heavier aqueous methanol-rich phase. 